The closed-form expressions in Theorem REF  do not rely on fast changing NLoS channel components, and do not involve computationally burdened integral and matrix inverse operators. Therefore, in contrast to time-consuming Monte-Carlo simulations, the evaluation of rate performance based on Theorem REF  can be computed rapidly. Besides, comparing the expressions in Theorem REF  with those in [1]}, one can see that the impact of imperfect CSI is fully characterized by the parameters \(e_{k1}, e_{k2}, e_{k3}\)  and \(\frac{\sigma ^{2}}{\tau p}\) . For the perfect CSI scenario without channel estimation error, we can assume \(\tau =\infty \) , which leads to \(e_{k1}=e_{k2}=e_{k3}=1\)  and \(\frac{\sigma ^{2}}{\tau p}=0\) .
